Exhaust gas analysis plays a significant part in the periodic testing of vehicles required by environmental protection laws and regulations. In addition to exhaust characteristics being demonstrative of engine operating characteristics, allowing the monitoring and measurement thereof, the percentages of particular exhaust gas constituents are subject to guidelines. The state of California has been a leader in establishing such guidelines, the most recent of which are codified in California BAR97 (Bureau of Automotive Repair) regulations.
Different test protocols and exhaust gas analyses require the sampling of the exhaust to be done in alternative manners. For percentage constituent analysis, for example, a small volume of exhaust gas, not contaminated or mixed with ambient air, can be captured and analyzed. This ordinarily requires capture of less than 1% of the tailpipe exhaust. For other tests where exhaust characteristics are reflective of differing engine operating parameters, the total of tailpipe exhaust is required to be sampled, often on an ongoing basis. Because of these differing requirements, the sampling apparatuses employed differ. Traditionally, separate constant volume and free flow collecting probes have been utilized, a test technician manually changing the probes as required during different phases of an integrated test procedure.
The current utilization of separate probes can affect the validity of test results. The manual interchange of probes does not prevent an exhaust sample from a first vehicle being used for one test, and the exhaust from a second vehicle, with a different probe, being used for a second test of a test protocol intended to be carried out for a single specific vehicle. In addition, because of the differing nature of the sampling techniques required, the different probes used are oriented and placed differently with respect to the exhaust system. The use of a plurality of probes, each one being required to be oriented separately and independently, increases the opportunity for improper placement and test error.
It is accordingly a purpose of the present invention to provide an exhaust probe apparatus which is capable of providing differing samples as required by different phases of an integrated vehicle testing protocol.
A further purpose of the present invention is to provide an integrated probe assembly which provides simultaneous independent sample outputs of differing types.
Yet a further purpose of the present invention is to provide a sampling probe which is efficient to use and economical in manufacture.